Elliot is the step brother of Gilbert Nightray and Vincent Nightray. Elliot is the only remaining biological son of the Nightray couples and is the heir to the Nightray family.

Elliot is hotheaded and outspoken, often acting crass towards people despite caring about them. He first meets Oz in the Ludwidge Academy library where they get into a fight over a character in the novel series "Holy Knight", denying the idea that self-sacrifice is ever justified or noble. He also despises how the Vessalius family seem to get away with anything just because they were heroes 100 years ago.

In later chapters, however, Elliot's hatred towards Oz has dissipated, and the two of them become good friends.

As a young child, Elliot was rather close to his elder brothers and sister. Being the youngest of the five Nightray children, he was often told to stay away from Vincent and Gilbert because the other Nightray children did not accept the two as their brothers. Elliot did not really know the reasons behind the hatred his older siblings felt for the other two, and so often he questioned why he was told to be careful around them. Elliot was the only Nightray child that seemed at ease with Vincent and Gilbert at a young age.

He was unknowingly made into Illegal Contracter with the Humpty Dumpty chain by Leo after the chain nearly killed him, carrying out murderous actions as the chain user without realizing. Upon learning the truth of his actions, he denied the chain at the cost of his life.